Magneto-mechanical resonators (MMR) are energized using a radio frequency source that generates a magnetic field. MMR sensors are based on the principles of magnetostriction and magneto-elastic coupling. Magnetostriction involves changing the shape of a ferromagnetic material when subjected to a magnetic field. Magneto-elastic coupling involves the relationship among the stress and strain of a material when subjected to a magnetic field.
Typically, a MMR sensor is coupled to an external magnetic field and receives magnetic energy from the magnetic field. The MMR sensor converts magnetic energy to mechanical oscillations. When the magnetic field is removed, the mechanical oscillations are converted to magnetic energy and the sensor radiates a magnetic field at a resonant frequency. A detector can then measure the radiated magnetic energy from the sensor. MMR can be used to construct wireless sensors to monitor environmental and biological variables.